Copywriting is writing copy for the purpose of advertising or marketing. The copy is meant to persuade someone to buy a product, or influence their beliefs.

Copywriters (known as continuity writers in broadcasting) are used to help create direct mail pieces, taglines, jinglelyrics, web page content (although if the purpose is not ultimately promotional, its author might prefer to be called a content writer), online ads, e-mail and other Internet content, television or radio commercial scripts, press releases, white papers, catalogs, billboards, brochures, postcards, sales letters, and other marketing communications media pages. In book publishing, flap copy and jacket flap copy describe the brief summary of a book which often appears on the inside of the book's hardcover dust jacket; back cover copy is similar, often briefer text placed on the book's outside back cover; catalog copy is another book summary maintained in a publisher's catalog of published books. Copy can also appear in social media content including blog posts, tweets, and social-networking site posts.

A copywriter usually works as part of a creative team. Advertising agencies partner copywriters with art directors. The copywriter has ultimate responsibility for the advertisement's verbal or textual content, which often includes receiving the copy information from the client. The copywriter is responsible for telling the story, crafting it in such a way that it resonates with the viewer/reader, ideally producing an emotional response. The art director has ultimate responsibility for visual communication and, particularly in the case of print work, may oversee production. Although, in many instances, either person may come up with the overall idea for the advertisement or commercial (typically referred to as the concept) and the process of collaboration often improves the work.

The Internet has expanded the range of copywriting opportunities to include web content, ads, emails, blogs, social media and other forms of electronic communications. Writing for the web is very different from writing for other media, tending to be more succinct than traditional advertising. Other stylistic nuances also come into play. It has also brought new opportunities for copywriters to learn their craft, conduct research and view others' work. The Internet has also made it easier for employers, copywriters and art directors to find each other.

As a consequence of these factors, along with increased use of independent contractors and virtual commuting generally, freelancing has become a more viable job option, particularly in certain copywriting specialties and markets.